Patient monitors are widely used in hospitals, especially in intensive care units and in premature infant wards. With such patient monitors one or typically multiple physiological variables are collected, processed if necessary and displayed to a user, like a care giver. Further, in general, patient monitors are also adapted for providing alarms if one or more of the collected variables exceed a respective predefined threshold.
A patient monitor is defined by comprising the following features:                Measure at least one physiological signal, and        Alarming capability for at least one measured signal and/or at least one interfaced physiological signal.        
Further, a patient monitor may comprise one or more of the following features:                At least one external signal to control external equipment, i.e. medical equipment for treating the patient.        User interface possibilities to visualize measured and interfaced physiological signals.        Trending possibilities for measured and interfaced physiological signals.        Possibilities to analyze actual and trended measured and interfaced physiological signals, i.e. with a clinical decision support system.        Possibilities to interact with the user and let the user enter data and comments of physiological and non-physiological data manually.        Infrastructure to transfer captured and processed data to a wired or wireless connected medical system solution, e.g. a central station, a hospital information system, an electronic medical record.        
A patient monitor does not have to be arranged in one single device common for all functions but can be a system with distributed units.
Further, physiological closed loop systems are known which use a patient variable for the control algorithm to calculate a signal for treating a patient. This often has the limitation that any disturbance on that specific patient signal results in either the inability to perform a control adjustment or, even worse, the control adjustment made is in the false direction. In a physiological closed loop system the transfer functions of a patient treating device with which a patient is treated, the patient itself and sometimes also the measurement of the patient variable are not constant and influenced by several external factors.
In principle, an automatic closed loop system shall reduce the work load of the care givers by partially replacing their actions with regard to the adjustments of the delivery of oxygen, medication or other treatment of the patient. However, actually regularly checking the patient's reactions to changes in the treatment of the patient are necessary, which is laborious for the care givers and can be annoying for the patient. For this and other reasons, the acceptance of the physiological closed loop systems is still low.